The Burroughs
Mine has produced very good, rich specimens of Samarskite-(Y) as well as
several other rare earth-element bearing minerals. The South Platte
District contains over 50 pegmatites, many of them known since the early
1920’s when they were first prospected for Feldspar. See the
accompanying photo of this locality, supplied by Rudy Bolona, a Colorado
mineral collector – nice looking place to go field collecting! The
three specimens available from the Burroughs Mine consist of solid black
massive Samarskite-(Y), without rock matrix or associated minerals. On a
fresh surface, the Samarskite-(Y) exhibits the characteristic, very
shiny glass-like luster and conchoidal fracture. Chemical composition
is: (Y,Fe3+,Fe2+,U,Th,Ca)2(Nb,Ta)2O8

ITEM
NO.

WEIGHT(GRAMS)

SPECIMEN SIZE(INCHES)

SPECIMEN
PRICE

2699

11.90

1 1/4

7/8

1/4

SOLD

2700

19.65

1 1/8

5/8

5/8

SOLD

2701

22.40

1 1/2

1/2

1/2

SOLD

2701

Burroughs Mine

2703
2704
2705
2706
2707

ALLANITE-(Ce)

Gunshot Prospect, Trout Creek Pass,
Chaffee County, Colorado

Specimens available are pure, fresh and
unweathered, dark brown Allanite-(Ce) masses with little or
no matrix. Chemical composition is: {CaCe}{Al2Fe2+}(Si2O7)(SiO4)O(OH)

Dark brown
massive Gadolinite-(Y) is present as pods and masses in matrix of
massive, pale tan color Yttrofluorite, which fluoresces very weak yellow
in SW UV light. Yttrofluorite is a variety of Fluorite
containing an appreciable amount of yttrium (Y) taking the place of
calcium (Ca) anions in the Fluorite structure. Very minor massive
Allanite-(Ce), plus secondary rare earth carbonate alteration phases,
are also present on some of the specimens. As shown in some of the
accompanying photos, a few of the small specimens have the massive
Gadolinite-(Y) surrounded by massive, red-brown “eyes” of Allanite-(Ce),
in / on Yttrofluorite matrix. Item 2717 is particularly rich, with a
large crystalline mass of Gadolinite-(Y) covering much of the surface of
the Yttrofluorite matrix. Price varies according to the richness of the
Gadolinite-(Y), not relative to the overall size of the specimen.

Samarskite-(Y) is an uncommon radioactive, uranium and rare earth
element bearing mineral with
the composition (Y,Fe3+,Fe2+,U,Th,Ca)2(Nb,Ta)2O8.
Samarskite-(Y) is very shiny brown-black on a freshly broken surface,
exhibiting conchoidal fracture, and has a dull luster on unbroken or
natural surfaces. The pegmatite deposits of the South Platte District
have been known since the 1920’s and worked for rare earth element
bearing minerals, and other minerals of economic importance, beginning
in the early 1950’s. These specimens were probably collected circa the
early 1970’s. Both specimens have masses of brown-black Samarskite-(Y)
with a minimal amount of matrix.

Samarskite-(Yb) was identified as a new species,
and a new member of the Samarskite group, from the Little Patsy
Pegmatite. It occurs as black, vitreous luster, metamict, anhedral
masses with a conchoidal fracture, sometimes intergrown with /
associated with Ferrocolumbite and Zircon Var. Cyrtolite. Other
minerals sometimes found associated are Ishikawaite, Samarskite-(Y),
Zircon, Columbite, Monazite-(Ce), and yttrian Fluorite (= Yttrofluorite).
A complete write-up covering this new member of the Samarskite group
appears in “The Canadian Mineralogist”, Vol. 44, pp. 1119-1125 (2006).
A copy of the 7 page write-up from “The Canadian Mineralogist” will be
sent with each specimen, if requested. All specimens were supplied by
one of the authors of the article. Note: The gram weights are given as
a measure of size -- specimens are not priced by the gram. The
simplified formula is:
(Yb,Y,REE,U,Th,Ca,Fe2+)(Nb,Ta,Ti)O4;

This is a
slightly different locality from the Gadolinite-(Y) with Yttrofluorite
mentioned above.
The collector who recovered these specimens notes that this occurrence
of REE minerals has not
been reported on MINDAT yet. Item 2722 has a group of two very crudely
developed, terminated,
dark brown-black Gadolinite-(Y) crystals on Fluorite Var. Yttrofluorite
matrix. Yttrofluorite is a variety of Fluorite containing an
appreciable amount of yttrium (Y) taking the place of calcium (Ca)
anions in the Fluorite structure. Item 2723 has several small, dark
brown masses of Gadolinite-(Y) on both sides of the specimen associated
with, and sometimes surrounded by massive, red-brown “eyes” of
Allanite-(Ce), on Yttrofluorite matrix.